Shock Spectrum Research Articles

Genomic expression profiling across the pediatric systemic inflammatory response syndrome, sepsis, and septic shock spectrum*

To advance our biological understanding of pediatric septic shock, we measured the genome-level expression profiles of critically ill children representing the systemic inflammatory response syndrome (SIRS), sepsis, and septic shock spectrum. Prospective observational study involving microarray-based bioinformatics. Multiple pediatric intensive care units in the United States. Children <or=10 years of age: 18 normal controls, 22 meeting criteria for SIRS, 32 meeting criteria for sepsis, and 67 meeting criteria for septic shock on day 1. The available day 3 samples included 20 patients still meeting sepsis criteria, 39 patients still meeting septic shock criteria, and 24 patients meeting the exclusive day 3 category, SIRS resolved. None other than standard care. Longitudinal analyses were focused on gene expression relative to control samples and patients having paired day 1 and day 3 samples. The longitudinal analysis focused on up-regulated genes revealed common patterns of up-regulated gene expression, primarily corresponding to inflammation and innate immunity, across all patient groups on day 1. These patterns of up-regulated gene expression persisted on day 3 in patients with septic shock, but not to the same degree in the other patient classes. The longitudinal analysis focused on down-regulated genes demonstrated gene repression corresponding to adaptive immunity-specific signaling pathways and was most prominent in patients with septic shock on days 1 and 3. Gene network analyses based on direct comparisons across the SIRS, sepsis, and septic shock spectrum, and all available patients in the database, demonstrated unique repression of gene networks in patients with septic shock corresponding to major histocompatibility complex antigen presentation. Finally, analyses focused on repression of genes corresponding to zinc-related biology demonstrated that this pattern of gene repression is unique to patients with septic shock. Although some common patterns of gene expression exist across the pediatric SIRS, sepsis, and septic shock spectrum, septic shock is particularly characterized by repression of genes corresponding to adaptive immunity and zinc-related biology.

선체부착형 원통형 배열 소나의 선체충격에 의한 응답

Dynamic response of a hull mounted sonar(HMS) to shocks transmitted through hull structures is analyzed and then the structural reliability of the sonars is evaluated. Finite element model of the hull mounted sonar is established and the transient responses to the shock is calculated using MSC.NASTRAN. According to BV043, the maximum allowable accelerations at the foundation of the sonar are converted from the shock spectra allowable for HMS. They are applied vertically and horizontally, respectively, using the large mass method. The structural reliability is evaluated by comparing the von-Mises stresses with the material yield stress. The drum for sensors shows a high reliability owing to mounts by which the shock waves from the base structure are well protected. However, the mounts between the base structure and the drum to mount sensors show a high stress intensity. The base structure also reveals a high stress intensity at the connection points to the hull.

The Hard X-ray Spectra of the Polars V2301 Oph, BL Hyi, and WW Hor

ABSTRACTThe hard X-ray spectra of the Polars V2301 Oph and BL Hyi acquired using the Proportional Counting Array (PCA) detector on board the Rossi X-ray Timing Explorer (RXTE) satellite were modeled using theoretical spectra from two-temperature radiative shock models for field-aligned accretion flows onto magnetic white dwarfs. The radiative shock models included the cooling processes e-i and e-e bremsstrahlung and Compton cooling and, importantly, self-consistently included the effects of cyclotron emission through an explicit solution of the radiative transfer equation rather than through the use of the approximate cyclotron cooling function derived by Chanmugam, Langer, and Shaviv. The spectra also included the effects of reflection from the surface of the white dwarf. We also discussed the eclipsing Polar WW Hor within the context of the theoretical shock models. WW Hor was observed and detected by XMM-Newton in the hard X-rays, and, unlike the above named Polars, WW Hor also exhibits an optical light curve with properties characteristic of a shock with cyclotron emission. We find that: (i) based on the X-ray continuum, the mass of the white dwarf in V2301 Oph is ) M⊙ for the known magnetic field strength B∗ = 7 MG. Using the observed optical flux of V2301 Oph, we set the further upper limit on the white dwarf mass of M∗ ∼ 1.2 M⊙. (ii) Based on the X-ray continuum and the shapes of the B and R optical light curves, we infer that the mass of the white dwarf in WW Hor to M∗ ≳ 0.4 M⊙ with magnetic field B∗ ∼ 15 MG. Using the observed optical flux of WW Hor, we suggest that the lower limit on the mass of the white dwarf mass in WW Hor is M∗ ∼ 0.8 M⊙. We were unable to model the hard X-ray spectrum of BL Hyi using a fitting function composed of an absorbed shock spectrum.

Vibro-impact attachments as shock absorbers

The use of vibro-impact (VI) attachments as shock absorbers is studied. By considering different configurations of primary linear oscillators with VI attachments, the capacity of these attachments to passively absorb and dissipate significant portions of shock energy applied to the primary systems is investigated. Parametric studies are performed to determine the dependence of energy dissipation by the VI attachment in terms of its parameters. Moreover, non-linear shock spectra are used to demonstrate that appropriately designed VI attachments can significantly reduce the maximum levels of vibration of primary systems over wide frequency ranges. This is in contrast to the classical linear vibration absorber, whose action is narrowband. In addition, it is shown that VI attachments can significantly reduce or even completely eliminate resonances appearing in the linear shock spectra, thus providing strong, robust, and broadband shock protection to the primary structures to which they are attached.

Analysis of transient vibrations on complex targets representing elementary configurations of GOCE satellite

Abstract In order to analyze the propagation of shocks due to hypervelocity impact of micrometeoroids and space debris on spacecrafts, it was necessary to analyze the high-frequency shock-propagation-dynamic on complex structures representative of real spacecraft structure. Objective of this research is the GOCE satellite due to its highly accurate accelerometer very sensitive to the micro-vibration environment. After a detailed analysis of the most-probable shock-propagation-path within the satellite, several representative targets have been designed. Then an extensive test campaign has been conducted on these targets exploring a wide range of impact conditions. As a result, a database was established which correlates the impact conditions in the experimental range (0.6–2.3 mm projectiles at 2.5–5 km/s) with the shock spectra on selected locations on various types of structural models. The behaviour of structural joints was also analyzed under shock conditions that are not normally reproduced by pyroshock testing. The database represent a fundamental tool in order to validate the numerical analysis that will be used to assess the vibration environment, due to in-orbit micrometeoroids and space debris at the accelerometer location. This paper presents the test procedure applied and the general results achieved.

EFFECT OF COMMONLY USED HERBICIDES ON THE VIRULENCE FACTOR CDR1 IN CANDIDA ALBICANS

The ubiquitous yeast Candida albicans becomes a troublesome pathogen by inducing virulence factors in response to environmental stimuli. Among these virulence factors is a drug-exporting transport protein, Cdrlp, which renders cells resistant to certain antifungal drugs. The expression of the CDR1 gene responds to a wide spectrum of stimuli, including drugs, heat shock, and steroid hormones. The aim of the present study is to characterize the effects of commonly used herbicides on the expression of CDR1. Following exposure of C. albicans cultures to varying doses of herbicides and azole drugs, CDR1 expression was quantified by flow cytometry using a reporter strain in which expression of a green fluorescent protein is under the control of the CDR1 promoter. Correlating CDR1 expression with cell growth and survival revealed that-similar to antifungal azole drugs-herbicides induce CDR1 expression only at inhibitory doses. It is concluded that none of the tested herbicides mimics the worrisome action of hormones, which increase virulence without reducing survival.

Diffusive Compression Acceleration of Energetic Particles with an Application to Shock Acceleration near Injection Energies

The behavior of energetic charged particles accelerated by a continuous plasma compression profile is explored in the framework of diffusion. At high enough energies, the accelerated particles have a power-law spectrum with a slope generally steeper than a shock spectrum with the same compression ratio. The spectral slope depends on the ratio of the diffusion coefficient to the product of the upstream plasma speed and the thickness of the compression region. In the limit of large diffusion, the spectrum becomes identical to that of diffusive shock acceleration, and when diffusion is small enough, it is consistent with adiabatic acceleration by a single passage through the compression region. For particles with a diffusion coefficient that increases with energy, the spectral shape of the accelerated particles changes from an adiabatic compressional acceleration spectrum at low energies to a shock spectrum at high energies. The flux level of the high-energy asymptotic shock spectrum is generally lower than that from a calculation with diffusive shock acceleration. When this result is applied to particles accelerated to high energies by shocks, the particle injection energy and efficiency can be determined once the energy dependence of the diffusion coefficient and the spectrum of the source particles are known. A threshold criterion for particle injection to shock acceleration can be set from the injection efficiency calculation.

Thermal infrared spectroscopy and modeling of experimentally shocked basalts

New measurements of thermal infrared emission spectra (250.1400 cm-1; ~7.40 μm) of experimentally shocked basalt and basaltic andesite (17.56 GPa) exhibit changes in spectral features with increasing pressure consistent with changes in the structure of plagioclase feldspars. Major spectral absorptions in unshocked rocks between 350.700 cm-1 (due to Si-O-Si octahedral bending vibrations) and between 1000.1250 cm-1 (due to Si-O antisymmetric stretch motions of the silica tetrahedra) transform at pressures >20.25 GPa to two broad spectral features centered near 950.1050 and 400.450 cm-1. Linear deconvolution models using spectral libraries composed of common mineral and glass spectra replicate the spectra of shocked basalt relatively well up to shock pressures of 20.25 GPa, above which model errors increase substantially, coincident with the onset of diaplectic glass formation in plagioclase. Inclusion of shocked feldspar spectra in the libraries improves fits for more highly shocked basalt. However, deconvolution models of the basaltic andesite select shocked feldspar end-members even for unshocked samples, likely caused by the higher primary glass content in the basaltic andesite sample.

Computationally Efficient Approaches to Characterize the Dynamic Response of Microstructures Under Mechanical Shock

We present computationally efficient models and approaches to simulate the response of microstructures under mechanical shock. These approaches include a Galerkin-based reduced-order model and a hybrid approach utilizing the response of structures to static loads combined with the dynamic shock spectrum of a spring-mass-damper system. To demonstrate the accuracy and efficiency of these approaches, we apply them on cantilever and clamped-clamped microbeams, and compare their predictions with analytical and finite-element (FE) results. We conclude that the hybrid approach is computationally efficient and accurate for microstructures behaving linearly in both quasi-static and dynamic loading conditions. The hybrid approach enables using simple analytical expressions that can be easily utilized by microelectromechanical system designers to judge the reliability of their devices. We show that reduced-order models are capable of capturing accurately the dynamic behavior of microstructures under shock pulses of various amplitudes (low-g and high-g), damping conditions, structural boundaries, and can capture linear and nonlinear behavior. Our results indicate that modeling the shock force as a quasi-static force for microstructures with low-natural frequencies may lead to erroneous results. High-g loading cases are investigated. Significant increase in the computational cost of simulations is reported when using traditional FE models because of the activation of higher order modes. The developed reduced-order model employing at least six modes is shown to be efficient in such cases. Design parameters are investigated to determine their effect on the shock resistance of microstructures. It is concluded that increasing air damping and tensile residual stresses improves the shock resistance of microstructures. A case study for the response of an optical fiber switch to shock is presented.

Shock excitation of the knots of Hen 3-1475

We present new optical STIS HST spectroscopic observations of the jets of the proto-planetary nebula Hen 3-1475. The excitation conditions of the knots of Hen 3-1475 are derived from the observed optical spectra, confirming that the knots are shock excited. The shocked spectra are qualitatively reproduced by simple ``3/2''D bow shock models. We present a set of bow shock models devoted to planetary nebulae, and discuss the effects of the pre-ionization conditions, the bow shock velocity, the bow shock shape and the chemical abundances on the predicted spectra. To explore the reliability of the ``3/2''D bow shock models, we also compare the observed spectra of other three proto-planetary nebulae (M 1-92, M 2-56 and CRL 618) to the predicted spectra.

Shocked plagioclase signatures in Thermal Emission Spectrometer data of Mars

The extensive impact cratering record on Mars combined with evidence from SNC meteorites suggests that a significant fraction of the surface is composed of materials subjected to variable shock pressures. Pressure-induced structural changes in minerals during high-pressure shock events alter their thermal infrared spectral emission features, particularly for feldspars, in a predictable fashion. To understand the degree to which the distribution and magnitude of shock effects influence martian surface mineralogy, we used standard spectral mineral libraries supplemented by laboratory spectra of experimentally shocked bytownite feldspar [Johnson, J.R., Hörz, F., Christensen, P., Lucey, P.G., 2002b. J. Geophys. Res. 107 (E10), doi:10.1029/2001JE001517] to deconvolve Thermal Emission Spectrometer (TES) data from six relatively large (>50 km) impact craters on Mars. We used both TES orbital data and TES mosaics (emission phase function sequences) to study local and regional areas near the craters, and compared the differences between models using single TES detector data and 3 × 2 detector-averaged data. Inclusion of shocked feldspar spectra in the deconvolution models consistently improved the rms errors compared to models in which the spectra were not used, and resulted in modeled shocked feldspar abundances of >15% in some regions. However, the magnitudes of model rms error improvements were within the noise equivalent rms errors for the TES instrument [Hamilton V., personal communication]. This suggests that while shocked feldspars may be a component of the regions studied, their presence cannot be conclusively demonstrated in the TES data analyzed here. If the distributions of shocked feldspars suggested by the models are real, the lack of spatial correlation to crater materials may reflect extensive aeolian mixing of martian regolith materials composed of variably shocked impact ejecta from both local and distant sources.

Ultrafast Shock Compression of Self-Assembled Monolayers: A Molecular Picture

Simulations of self-assembled monolayers (SAMs) are performed to interpret experimental measurements of ultrafast approximately 1 GPa (volume compression deltaV approximately 0.1) planar shock compression dynamics probed by vibrational sum-frequency generation (SFG) spectroscopy (Lagutchev, A. S.; Patterson, J. E.; Huang, W.; Dlott, D. D. J. Phys. Chem. B 2005, 109, XXXX). The SAMs investigated are octadecanethiol (ODT) and pentadecanethiol (PDT) on Au(111) and Ag(111) substrates, and benzyl mercaptan (BMT) on Au(111). In the alkane SAMs, SFG is sensitive to the instantaneous orientation of the terminal methyl; in BMT it is sensitive to the phenyl orientation. Computed structures of alkane SAMs are in good agreement with experiment. In alkanes, the energies of gauche defects increase with increasing number and depth below the methyl plane, with the exception of ODT/Au where both single and double gauche defects at the two uppermost dihedrals have similar energies. Simulations of isothermal uniaxial compression of SAM lattices show that chain and methyl tilting is predominant in PDT/Au, ODT/Ag and PDT/Ag, whereas single and double gauche defect formation is predominant in ODT/Au. Time-resolved shock data showing transient SFG signal loss of ODT/Au and PDT/Au are fit by calculations of the terminal group orientations as a function of deltaV and their contributions to the SFG hyperpolarizability. The highly elastic response of PDT/Au results from shock-generated methyl and chain tilting. The viscoelastic response of ODT/Au results from shock generation of single and double gauche defects. Isothermal compression simulations help explain and fit the time dependence of shock spectra but generally underestimate the magnitude of SFG signal loss because they do not include effects of high-strain-rate dynamics and shock front and surface irregularities.

Heliospheric energetic neutral atoms as a means to determine the anomalous cosmic ray spectrum at the termination shock

We demonstrate the possibility of deriving the anomalous cosmic ray (ACR) spectrum at the solar wind termination shock and the strength of the shock using energetic neutral H and He atoms (ENA) measurements at 1 AU. Assuming that the energetic neutral atoms detected by CELIAS/HSTOF on board SOHO are of ACR origin, we consider fits to the ACR termination shock spectrum based on approximations to the ACR distribution downstream of the shock. We show that the method becomes much more effective when the low-energy ENA data are combined with the available high-energy ACR data from Voyager spacecraft. The results imply a weak termination shock (compression ratio ).

A New Look at Stellar Outflows: Spitzer Observations of the HH 46/47 System

We present the Early Release Observations of the HH 46/47 system and HH 46 IRS 1 source, taken with the three instruments aboard the Spitzer Space Telescope. The optically invisible southwest lobe, driven by the HH 47C bow shock, is revealed in full detail by the Infrared Array Camera (IRAC) images and displays a 'loop'-like morphology. Both of the mid-infrared outflow lobes are narrower than those of CO flow. We believe that the combination of emission by H2 rotational lines [S(11)-S(4)] and some atomic lines, which fall within the IRAC passbands, are responsible for the bulk of the observed emission, although contributions from the 3.3, 6.2, and 7.7 micron polycyclic aromatic hydrocarbon emission bands cannot be ruled out. Weak spectral features corresponding to these emitters are present in the Infrared Spectrograph spectrum of the HH 47A bow shock. The spectrum of HH 46 IRS 1 shows remarkable similarities to those of high-mass protostars, which include the presence of H2O, CO2, CH4, and possibly NH3, CH3OH, and ices. The high ice abundances and the lack of signs of thermal processing indicate that these ices in the envelope are well shielded from the powerful outflow and its cavity. Emission from the Bok globule at 24 micron is detected and displays a similar structure to that observed at 8 micron.

M c Neil's Nebula in Orion: The Outburst History

We present a sequence of I-band images obtained at the Venezuela 1 m Schmidt telescope during the outburst of the nebula recently discovered by J. W. McNeil in the Orion L1630 molecular cloud. We derive photometry spanning the preoutburst state and the brightening itself, which is a unique record including 14 epochs and spanning a timescale of ~5 years. We constrain the beginning of the outburst at some time between 2003 October 28 and November 15. The light curve of the object at the vertex of the nebula, the likely exciting source of the outburst, reveals that it has brightened ~5 mag in about 4 months. The timescale for the nebula to develop is consistent with the light-travel time, indicating that we are observing light from the central source scattered by the ambient cloud into the line of sight. We also show recent FLWO optical spectroscopy of the exciting source and of the nearby HH 22. The spectrum of the source is highly reddened; in contrast, the spectrum of HH 22 shows a shock spectrum superposed on a continuum, most likely the result of reflected light from the exciting source reaching the HH object through a much less reddened path. The blue portion of this spectrum is consistent with an early B spectral type, similar to the early outburst spectrum of the FU Orionis variable star V1057 Cygni; we estimate a luminosity of L ~ 219 L☉. The eruptive behavior of McNeil's Nebula, its spectroscopic characteristics and luminosity, suggest that we may be witnessing an FU Ori event on its way to maximum. By further monitoring this object, we will be able decide whether or not it qualifies as a member of this rare class of objects.

Modulation and acceleration of anomalous protons in the outer heliosphere

A comprehensive time-dependent modulation model including particle drifts, enhanced perpendicular diffusion, a solar wind termination shock (TS), and a heliosheath is used to study the acceleration and modulation of anomalous protons in the outer heliosphere. It is shown how the spectral forms of the accelerated anomalous protons at 90 AU change for the two heliospheric magnetic field polarity configurations during solar minimum conditions. Further, it is shown how these shocked spectra are modified and modulated in the outer heliosphere if the compression ratio of the TS was changed. The compression ratio is found to be by far the most dominant modulation factor.

Thermal infrared spectroscopy and modeling of experimentally shocked plagioclase feldspars

Thermal infrared emission and reflectance spectra (250-1400 cm-1; ~7-40 mm) of experimentally shocked albite- and anorthite-rich rocks (17-56 GPa) demonstrate that plagioclase feldspars exhibit characteristic degradations in spectral features with increasing pressure. New measurements of albite (Ab 98 ) presented here display major spectral absorptions between 1000-1250 cm -1 (8-10 mm) (due to Si-O antisymmetric stretch motions of the silica tetrahedra) and weaker absorptions between 350-700 cm -1 (14-29 mm) (due to Si-O-Si octahedral bending vibrations). Many of these features persist to higher pressures compared to similar features in measurements of shocked anorthite, consistent with previous thermal infrared absorption studies of shocked feldspars. A transparency feature at 855 cm -1 (11.7 μm) observed in powdered albite spectra also degrades with increasing pressure, similar to the 830 cm-1 (12.0 μm) transparency feature in spectra of powders of shocked anorthite. Linear deconvolution models demonstrate that combinations of common mineral and glass spectra can replicate the spectra of shocked anorthite relatively well until shock pressures of 20-25 GPa, above which model errors increase substantially, coincident with the onset of diaplectic glass formation. Albite deconvolutions exhibit higher errors overall but do not change significantly with pressure, likely because certain clay minerals selected by the model exhibit absorption features similar to those in highly shocked albite. The implication for deconvolution of thermal infrared spectra of planetary surfaces (or laboratory spectra of samples) is that the use of highly shocked anorthite spectra in end-member libraries could be helpful in identifying highly shocked calcic plagioclase feldspars.

Shock spectra and damage boundary curves for hyperbolic tangent cushioning system and their important features

AbstractBy applying the method suggested in the author's previous paper, shock spectra and damage boundary curves are investigated for a hyperbolic tangent cushioning system under the action of rectangular, half‐sine, terminal‐peak saw‐tooth and initial‐peak saw‐tooth acceleration pulses, respectively. The shock spectrum is affected not only by the damping parameter but also by the dimensionless pulse peak, and both the damping parameter and the dimensionless fragility influence the damage boundary curve for this cushioning system. Some important features of a hyperbolic tangent cushioning system that differs from a tangent cushioning system are discussed in detail. Copyright © 2001 John Wiley &amp; Sons, Ltd.

Resonance‐Line Scattering in Supernova Remnant Shocks

We present a three-dimensional radiative transfer model to examine the effects of resonance-line scattering in the postshock flow behind a nonradiative supernova remnant shock. For a rippled shock front viewed edge-on, line scattering significantly reduces the observed flux of C IV λ1549 and N V λ1240, two important diagnostic lines in the ultraviolet spectra of supernova remnants. The correction factor (defined to be the ratio of the line flux that would be observed neglecting scattering to the actual observed line flux) is a function of position within the filament. For sufficiently large regions that include crisp edges as well as more diffuse regions of the filament structure, the C IV and N V correction factors are between about 1.5 and 3.5 (and the C IV correction factor is invariably larger than the N V correction factor). The correction factors have a larger range when smaller regions are considered. The C IV correction factor is about 6 at the filament edges, while the N V correction factor is about 4. These simulations of resonance-line scattering will be useful for the analysis of supernova remnant shock spectra.

Seismic Performance of Direct Hung Suspended Ceiling Systems

Current seismic design philosophies require an earthquake-resistant building capable of resisting strong motion for structures and nonstructural elements. In response to the need to understand the seismic behavior of nonstructural elements, this paper presents the study on the vibration behavior and seismic capacity of direct hung suspended (DHS) ceiling systems. Modal analysis to investigate the eigen properties of the DHS ceilings was performed. Natural frequencies and mode shapes were identified using analytical models and verified by modal experiments. Different ceiling configurations were tested to understand their ultimate strength under incremental shock spectrum excitation. It was discovered that the 45° sway wires method prescribed by ceiling and Interior System Contractors, does not increase the seismic capacity of the entire system. Based on recent field observations of DHS ceiling earthquake damage in Taiwan, it was found that pop rivets at the molding would increase the seismic capacity of the DHS systems. It was also discovered that a constraint transverse to the excitation direction would greatly influence the behavior of a DHS system.